Conventionally, a method (a block caving method) for widely cutting out a lower portion of a mineral deposit and collapsing the whole mineral deposit to a surface of the ground and picking ores out of the lower portion has received attention from an economic standpoint with deepening of the mineral deposit.
Conventionally, various devices or techniques have been proposed in order to detect and analyze an abnormality of the inside of a stratum, a mineral deposit or a tunnel. A technique for forming a pressure measurement probe installed in an artificial crack formed in an underground excavation borehole and monitoring displacement of a tunnel is disclosed in the following PTL 1. A technique for measuring displacement of a surface of a block of rock is disclosed in the following PTL 2. A technique for applying a magnetic field to a high-speed magnetic fluid injected into an investigation pit and analyzing an underground fracture structure is disclosed in the following PTL 3.